The overall objective of this project is to understand how the number of taste buds in a region of the mouth influences the quality and intensity of taste sensation. This goal would permit a new perspective on the quantification of taste perception and provide a method for better evaluation of patients with taste dysfunction. We have shown that the density of taste buds in fungiform papillae varies by more than 100 times among normal subjects. This variation is consistent in individuals for two regions: the tip and midregion. Behavioral experiments have shown that taste sensitivity also varies between these regions, and papillae with more taste buds produce a wider range of taste qualities and taste intensity. A method has been developed using videomicroscopy for counting taste pores in living rabbits. A pore is the opening of a taste bud onto the surface of a papilla. Using the new method to examine rabbit tongues, we have found that the number and distribution of taste buds is changing in adult rabbits. It is proposed to count taste pores in rabbits at varied intervals to determine the proportion of taste pores that change and the rate of change. It is also proposed to use the method to quantify human fungiform taste pores and to see if the number of taste pores on human papillae is changing. If the density of taste buds changes, then we would expect some periodic change in taste sensitivity. The circumvallate and foliate taste buds will be counted in sections of human cadaver tongues on which fungiform taste bud density has been quantified. Topological examination with videomicroscopy is not possible because the taste buds are in troughs. By using subjects with high and low taste bud densities, taste bud densities will be compared by rank order among regions and subjects. If the relative densities are correlated among regions, it will suggest that the factors which control taste bud density are systemic. If the relative densities are disparate among regions, it will suggest that local factors such as the innervation or epithelium predominate. Since there is behavioral evidence for the genetic regulation of taste sensitivity, the relative taste bud density may be influenced by genetic factors. Changing tastes in humans may be due to changing taste bud populations.